1. Field of the Invention
The present invention relates to a system for heating, bending and cooling of glass.
2. Prior Art
A mold system used in the bending of glass has been described in U.S. Pat. No. 2,526,359. In this mold system, the bending mold is convex upwards and when the glass sheet is lowered over the mold, the glass sheet is supported by central parts of the mold. The mold includes two side template plates which position the pipes forming the mold at the desired bending curvature. The pipes are separated from each other at a constant distance by vertical members and the pipes can only move in vertical direction. The "pipe" mold is supported in its center by a brace, which can give support only in a vertical direction. To produce a desired shape of glass, the template plates and the middle located brace are replaced with templates and a brace, which are formed to give a desired shape of glass.
In U.S. Pat. No. 2,223,124 a method is described in which a horizontal glass plate is placed on a roll device, which in the beginning has horizontal rolls which are separately supported and are spaced apart from each other. While the glass is heated, these rolls are incrementally lowered and while these rolls are lowered, they give shape to the glass. By varying guidance of the rolls, one can produce different kind of shapes.
The aforementioned glass bending methods have many problems. In both methods the mold needs a heavy frame construction which causes a great deal of difficulty, because the frame is located in the oven, which is both heated and cooled.
In the construction shown in U.S. Pat. No. 2,256,359, the pipes have to be unbending, they are also heavy, because they are supported in axial direction only at their ends and in the middle they are only carried. The frame of the mold is not adjustable and the pipes used have to be full length even in case of small glass sheet bending. In a heavy mold different parts may warm up at different times and they may even remain at different temperatures, which causes distortions. Because the pipes are not supported in axial direction in the middle, it is particularly easy to get distortions in pipes.
In the construction shown in U.S. Pat. No. 2,223,124 it is troublesome to guide lowering of the roll devices, which is a very difficult operation and which must be done inside the oven. Because of construction of the roll device it is also impossible to make the mold smaller in any simple way when it is used with smaller glass sizes. In addition to this there is a special difficulty in using rolls, because this is done in a hot environment (about 600 .degree. C.) and shape of the roll devices is changing all the time.
The heating, bending and cooling system according to present invention provides a significant improvement over the prior art molds.